Under Shirk, the institute has gained prominence as a center for the study of Mexico and of cross-border issues. Just days before his March 27 resignation, Shirk was in Washington, D.C., testifying about border security before a Senate committee.

Shirk “will return to his full-time faculty position in the Department of Political Science and International Relations in the College of Arts and Sciences,” according to a written message from Edward Luck, the new dean of the university’s Joan B. Kroc School of Peace Studies, which oversees the institute.

Luck’s message was delivered in an institute newsletter on Thursday, and stated that “David has led the institute through a decade of substantial growth in terms of its reach, influence and visibility.”

No reason was given for his resignation. Neither Luck nor Shirk could be reached Thursday.

“David set the gold standard for research on rule of law issues in Mexico and cooperation between the two countries,” said Andrew Selee, vice president for programs and formerly director of the Mexico Institute at the Wilson Center in Washington, D.C. “He will continue to do so.”

Elsa Saxod, who once headed San Diego’s border affairs office and is a member of the Trans-Border Institute’s advisory council, said Shirk’s departure “is a loss to the Trans-Border Institute and a loss to the binational region.”

Shirk “will leave big shoes to fill,” said Tijuana attorney José Larroque, also a council member. The institute “has become a go-to place for information on crime and justice along the border and in Mexico," and “has been instrumental in the training of judges and attorneys on the handling of oral trials deriving from reforms to the justice system,”Larroque said.